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G. LEGH & H.- W. MACLEAR.

SURVEYING INSTRUMENT No. 554,190.- Patented Feb. 4, 1896.

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NITED STATES ATENT OFFICE.

SURVEYING-INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 554,190, dated February 4, 1896.. Application filed August 1,1895. Serial No. 56 7,885. (No model.)

To all whom it may concern:

Be it known that we, GILBERT LEGH, residing at 8 Cadogan Square, and HENRY WVAL- LIOH MAOLEAR, residing at 42 Holbein House, Sloane Square, London, England, citizens of England, have invented a Surveying-Instruin cut, of which the followingis a specification.

This invention relates to a convenientlyportable surveying instrument, especially suitable for military surveying, as we shall describe, referring to the accompanying drawings.

Figure 1 is a perspective showing the case closed. Fig. 2 shows it open in condition for observing an azimuth or hearing. Fig. 3 is a plan, and Fig. 4 a transverse section, of the protractor employed. Fig. 5 is a plan showin g the protract-or in the case with guide-bar set, and Fig. 6 is a perspective showing the protractor and case applied as a clinometer.

In a case A,which may be of wood, provided with alid B, hinged to it, we accommodate a removable protractor 0, preferably made of transparent material, such as celluloid, and having mounted in it a magnetic needle 0, over which is a glass 0, marked with two diametral lines N S and W E crossing each other at right angles. The glass so marked is held in a rim 0 which can be turned round, so as to bring the line E, when required to coincide with a line 0 marked on the protractor, parallel to its straight edge. The degree divisions are preferably numbered both ways for convenience of reading from both ends. In the straight side of the protractor we accommodate three scales 0 any one of which can be brought to the front. These being graduated on both sides furnish six scales for plotting or reading maps or plans. There might, however, be a greater or less number of such scales, which are held in place by a turnbuckle c The case A has pivoted on one side a barD, with a pin d projecting upward from its middle, on which, when turned so as to cross the case, as shown in Fig. 2, can be engaged an eye 0, provided at the center of the straight side of the protractor. At the front of the case is pivoted an eyepiece F, which can be turned up to take avertical position when the lid is raised, as shown inFig. 2.

The lid B itself has a long central slot, which may have awire or thin metal strip 2) stretched along it to form a sight-line, and on each side of the slot is fixed a mirror I).

For taking a bearing or azimuth a sight is taken through the eyepiece F and past the sight-line, and the protractor is turned on the pin (1 until the needle points to N, as can be seen by the observer in the mirror I). The bearing of the object is then determined by the graduation of the protractor, which. coincides with the fiducial line a.

As shown in Fig. 5, the bar D can be set to any graduation of the protractor while the needle points to N, so that the operator can proceed in any determined direction. In order that he may thus be guided at night the bottom of the case is lined with paper or other material coated with luminous paint.

For employing the instrument as a clinometer, as shown in Fig. 6, the eye 0 of the protractor is engaged on a pin 19 projecting from the lid. The ends of the protractor are held between the finger and thumb, leaving the lid and case to hang freely while a sight is taken along the straight edge, of the protractor at an object, the depression or elevation of which is determined by the graduation which coincides with the sight-line b.

Having thus described the nature of our invention and the best means we know for carrying the same into practical effect, we claim A surveying-instrument comprising a removable protractor having a straight edge provided with a magnetic needle and a case for the protractor having a lid hinged to it, the said case being provided with an eyepiece and cross-bar pivoted to its sides and the said lid being provided with a sight-line and mirror substantially as described.

In testimony whereof We have signed our names to this specification, in the presence of two subscribing witnesses, this 17th day of July, A. D. 1895.

GILBERT LEGH. HENRY W. MAGLEAR. 

